Biomedical subjects

Hajime Kumagai

Publications and source records attributed to Hajime Kumagai.

8 recordsLinked to original sources

PubMed2006

Intra-aortic injection of propofol prevents spinal cord injury during aortic surgery.

OBJECTIVE: We investigated whether propofol, a widely used anesthetic, injected into clamped aortic segments quickly attenuated transcranial spinal motor-evoked potential (MEP) amplitudes and protected against spinal cord injury during thoracoabdominal aortic surgery. METHODS: Eighteen beagle dogs were divided into three groups (n=6, each group): group 1 (20 ml of saline, intra-aortic injection), group 2 (1.5 mg/kg of propofol, intravenous injection), and group 3 (1.5 mg/kg of propofol, intra-aortic injection). Aortic cross-clamping was performed for 30 min. In each group, MEP amplitudes were recorded before, during, and after aortic cross-clamping. Tarlov score and histopathological examination were used to evaluate the protective effects of intra-aortic propofol injections. RESULTS: MEP amplitudes in group 3 attenuated to a value that was 60% of the control in just a minute after aortic cross-clamping, but maintained 40% of the control value during aortic cross-clamping. However, MEP amplitudes in groups 1 and 2 gradually attenuated and almost disappeared. Groups 1 and 2 amplitudes were lower than those in group 3, 30 min after aortic cross-clamping (p<0.001). Twenty-four hours after ischemia, the Tarlov score in group 3 was 3.5+/-0.5 and was higher than scores from groups 1 and 2, which were 0.5+/-0.5 and 1.3+/-1.2 (mean+/-SD, p<0.001, and p<0.001), respectively. Histopathologically, normal spinal cord motor neurons in group 3 were preserved to a significantly greater extent than in groups 1 and 2 (p=0.0031, and p=0.0282, respectively). There was a strong correlation between Tarlov scores at 24h and the number of normal motor neurons in the anterior horns of spinal cords (r=0.897; p<0.001). CONCLUSIONS: Intra-aortic propofol injections produce the quick suppression of MEP amplitudes and protect spinal cords from ischemia during aortic cross-clamping.

Animals↗

PubMed2006

Cold spinoplegia and transvertebral cooling pad reduce spinal cord injury during thoracoabdominal aortic surgery.

OBJECTIVE: We examined the protective effects of the new selective spinal cord cooling by using cold saline infusion into the cross-clamped aorta and a transvertebral cooling pad placed over the lumbar vertebral column from paraplegia caused by ischemic spinal cord injury on thoracoabdominal aortic surgery. METHODS: Eighteen rabbits were divided into three groups: groups I, II, and III (n = 6 for each group). In group I (37 degrees C; 5 mL) and group II (3 degrees C; 5 mL), saline was infused into the isolated aortic segment twice, at 0 and 5 minutes after aortic cross clamping. In group III, a 3 degrees C saline solution plus cooling pads placed just after cross clamping were combined. The infrarenal aorta was then isolated proximally and distally by vascular clamps for 12 minutes. In our preliminary study, only the abdominal aorta just distal to the left renal artery was clamped. At 48 hours after reperfusion, the groups clamped for 12 and 15 minutes were all paraplegic. The time of clamping the aorta was set at 12 minutes as the critical point when paraplegia occurred upon simple clamping of the infrarenal aorta only. The spinal cord temperature was monitored at the L4 level continuously during the procedures in all three groups. At 8, 24, and 48 hours after the operation, hind limb function was estimated by using the Tarlov score, which is often used for evaluating motor function in animals. A histopathologic study using hematoxylin and eosin stains was also performed. RESULTS: At 48 hours after the operation, the Tarlov scores in groups I, II, and III were 0 +/- 0, 2.0 +/- 1.9, and 4.0 +/- 0 (mean +/- SD), respectively. The Tarlov score and histopathologic analysis in group III were significantly superior to those of groups I (P < .01) and II (P < .05). The spinal cord temperature in groups II and III decreased by -1.8 degrees C and -4.3 degrees C at its minimum. The rabbits in group III were also protected from paraplegia. CONCLUSIONS: Selective spinal cord cooling with cold saline infusion into the isolated aortic segment and transvertebral regional cooling can reduce the neurologic damage of spinal cord ischemia.

Animals↗

PubMed2006

Evoked spinal cord potentials monitored at thoracoabdominal region after trans-intercostal stimulation.

To investigate the feasibility of a novel recording method for trans-intercostal evoked spinal cord potentials (Tic-ESCPs) and the properties of the waveforms, the potentials were recorded and analyzed in an animal model. In two beagle dogs, Tic-ESCPs were recorded at the left twelfth intercostal to fourth lumbar nerves following stimulation at the left eleventh intercostal nerve, either with or without the use of a muscle relaxant. The amplitude and latency of the Tic-ESCP waves were then measured and compared with those of conventional transcranial spinal motor evoked potentials (MEPs). Tic-ESCPs could be obtained at any nerve, with or without the use of a muscle relaxant. The Tic-ESCP waveform was clear and simple, consisting of a small positive (P1) wave and a subsequent large negative (N1) wave. As the site of recording moved farther from the stimulation site, the N1 amplitudes were reduced and the P1 latency was prolonged. Under muscle relaxation, the N1 amplitudes were reduced, and the P1 latencies were shorter. As compared with MEPs, Tic-ESCPs could be evoked by a weaker stimulus, the N1 amplitude was smaller, and the P1 latency was shorter. Tic-ESCP recording was feasible either with or without the use of a muscle relaxant. The Tic-ESCPs showed simple and clear waveforms with smaller stimulations. Therefore, Tic-ESCPs may be useful for intraoperative spinal cord monitoring.

Abdomen↗

PubMed2005

A novel canine model of spinal cord ischemia with reproducible neurologic outcomes.

PURPOSE: To develop a canine model of spinal cord ischemia (SCI) with highly reproducible neurologic outcomes. METHODS: Spinal cord ischemia was induced by cross-clamping the proximal descending aorta. To produce substantial ischemia in the critical lumbar region, the proximal aortic blood pressure (PAP) was reduced to 80 mmHg by withdrawing blood into a reservoir connected to the left subclavian artery. We conducted an intraischemia spinal cord electrophysiologic study and a postischemia assessment of hindlimb motor function in six animals subjected to this procedure with an aortic occlusion time of 40 min, and in six animals subjected only to aortic occlusion for 60 min. RESULTS: All the animals subjected to this procedure exhibited a significant decrease in motor-evoked spinal cord potentials to transcranial electric stimulation (MEPs) during the acute ischemic phase, and they were paraplegic 48 h after ischemia. In contrast, two of the animals not subjected to PAP reduction showed complete functional recovery with intact MEP findings. CONCLUSION: This model is feasible for experimental SCI studies because it can reliably and easily reproduce substantial ischemia.

Animals↗

PubMed2005

Echo-guided identification of key lumbar arteries for the spinal cord: preliminary study in the canine model.

Although identification of the key artery that perfuses the spinal cord is essential to avoid occurrence of paraplegia after surgery on the thoracoabdominal aorta, reliable and noncomplicated measures are not yet available. A new method of determining it by using echocardiography with a saline injection into the lumbar artery was evaluated for feasibility and adequacy in a canine model. In two mongrel dogs, the abdominal aorta was opened and saline was directly injected into the lumbar arteries while the spinal cord was visualized by echocardiography through the intervertebral disc. When the echogenic or Doppler signal was detected in the spinal cord, the particular lumbar artery was determined as "positive", or as "negative" when the signal was not detected. After the dog was sacrificed, red resin was injected into the "positive" arteries and blue resin into the "negative" arteries. In the extracted spinal cord, the anterior and posterior spinal arteries were filled with red resin, rather than with blue resin, to indicate that the key arteries were correctly identified. There were multiple "positive" arteries, which were mainly located on the left side and accounted for approximately one-third of the entire lumbar arteries. The "negative" arteries mainly perfused the muscles around the vertebra. Injected resin came out of the adjacent lumbar arteries of the same category, suggesting that communication is present among the positive arteries, but independently of that among the negative arteries. Echo-guided identification of key arteries is technically feasible and correctly determines the key arteries in this preliminary canine model.

Animals↗

PubMed2005

Cold saline injection attenuates motor-evoked potential in the spinal cord by cortical electrical stimulation in the dog.

Changes in the motor-evoked potential of the spinal cord with transcranial stimulation are monitored for spinal cord function during thoracoabdominal aortic aneurysm surgeries. We examined the effects of changes in motor-evoked potential with cold saline injected into the clamped segment of the aorta, and compared the effects to lidocaine and warm saline injection. Eighteen dogs were divided into three groups according to the injected agents: Warm saline group (37 degrees C, 20 ml), Cold saline group (4 degrees C, 20 ml), and Lidocaine group (5.0 mg/kg of lidocaine in 20 ml of warm saline), (n=6, each group). Changes in the peak-to-peak MEP amplitude and the indirect wave (I wave) amplitude were measured during aortic cross-clamping. In the peak-to-peak MEP amplitude, the cold saline and lidocaine groups attenuated to 80% of the control value but were not significantly changed. In the I wave amplitude, the cold saline group showed a significant attenuation 1 min after injection (p<0.0001) and the lidocaine group 4 min after injection (p=0.0230), when compared with the warm saline group. Attenuation of the I wave amplitude in the cold saline group was significantly larger than that in the lidocaine group (p=0.0003). Changes in the I wave amplitude appeared within 4 min in both the cold saline and lidocaine groups. Cold saline injection into the clamped segment of the aorta is a diagnostic procedure for determining presiding critical arteries in the segment without experiencing the pharmacological side effects observed with lidocaine injection.

Animals↗

PubMed2005

Echo-guided identification of key lumbar arteries supplying the spinal cord in a canine model.

The aim of this study was to anatomically verify echo-guided identification of key lumbar arteries supplying blood to the spinal cord and to examine whether changes in nerve root motion could be used for detecting malperfusion following aortic cross-clamping. In two beagle dogs, nerve root motion was monitored through the intervertebral disc using transesophageal echocardiography. Communications between each lumbar artery and the spinal vasculature were assessed by echogenic signals in the spinal cord following saline injection into each lumbar artery. Nerve root motion immediately disappeared after clamping the aorta and recovered as soon as it was declamped. These changes were induced specifically by clamping the aorta at the first lumbar level. The changes were instantaneous and may be beneficial because of minimal ischemic insult of the spinal cord. In dog #1, the result of the saline injection test was anatomically verified with the presence of a spinal branch. However, in dog #2 echogenic signals appeared in the muscles as well as in the spinal artery. A morphological study showed no spinal branch of the lumbar artery but only an indistinct artery in the intervertebral foramen. These findings probably account for those cases in humans where there is unsuccessful visualization of the Adamkiewicz artery by angiography. Consequently, the above two assessments identified the key artery. Cessation of nerve root motion following segmental clamping of the aorta and echogenic signals in the spinal cord following saline injection into a lumbar artery may represent the key artery with respect to hemodynamics and perfusion, respectively.

Animals↗

PubMed2002

Gigantic thymolipoma.

A 48-year-old woman with an abnormal shadow in chest radiography during an annual physical examination was found by chest computed tomography to have a large fatty mass lesion found to be diagnosed as a gigantic lipoma. Histopathological diagnosis was found to be benign thymolipoma consisting of mature fatty tissue and hyperplastic thymic tissue structures with Hassall,s corpuscles. Although the diagnosis is supported by imaging studies that demonstrate fat and soft tissue within the tumor, variations occur in computed tomography appearance. We suggest that surgical excision be considered when a gigantic intrathoracic lipomatous mass is in scanning as in this case.

Female↗